A commentary on “Methodological appraisal of the evidence about efficacy of metabolic surgery in adults with nonmorbid obesity and hypertension: an overview of systematic reviews”
Authors: Xintian Shou, Yumeng Wang, Yuanhui Hu
Journal: International Journal of Surgery (2023)

We read with interest the article by Cáceres-Távara et al1. The authors provided a useful assessment of the quality of evidence regarding the efficacy of metabolic surgery in adults with nonmorbid obesity and hypertension. It is an interesting topic that metabolic surgery can reduce blood pressure. The authors noted that the three included systematic reviews may not have captured studies on hypertension patients without diabetes, which did not fully match their research purpose, leading to bias. The authors also found that the cases included in the three systematic reviews were not assessed according to the standardized quality assessment criteria (AMSTAR-II), which could also lead to bias. What’s more, the lack of detailed criteria for evaluating the success in reducing blood pressure also led to uncertainty. Thus, very low levels of confidence and certainty were observed in all three systematic reviews as described by the authors. We highly agree with the above methodological appraisal results proposed by the authors. However, we have some concerns and suggestions. There are many confounding factors affecting the authenticity and accuracy of clinical research results of hypertension. We noted that the studies included in the three systematic reviews only adjusted for confounding factors such as blood lipid level, glycosylated hemoglobin, and waist circumference, while ignoring medical history information such as obstructive sleep apnea (OSA). OSA is an independent risk factor for hypertension. Intermittent hypoxia in OSA promotes endothelial dysfunction, sympathetic nervous system activation, which are related to the pathogenesis of hypertension2. Obesity has been recognized as one of the strongest risk factors for OSA. The study has shown that OSA is highly prevalent in both morbid obese patients with a body mass index greater than 40 kg/m2 and nonmorbid obese people with a body mass index less than 40 kg/m23. Nonmorbid obesity, hypertension, and OSA are closely related and interact, forming a dangerous triad. Metabolic surgery for nonmorbid obesity can not only reduce blood pressure but also alleviate OSA. Therefore, it is uncertain whether the beneficial changes in blood pressure after metabolic surgery are due to the surgery itself or the relief of OSA. We suggest that other confounders of hypertension represented by OSA should also be investigated and considered during quality evaluation, as they can affect the confidence and certainty of the three systematic reviews. The authors’ consideration of the type of bariatric surgery techniques should not be overlooked. Roux-en-Y gastric bypass separates a portion of the stomach as a small gastric sac and anastomoses it with the middle of the jejunum to form the Roux or digestive limb4. The sleeve gastrectomy vertically excises the fundus and body of the stomach, reducing gastric volume4. Study shows that Roux-en-Y gastric bypass exhibits superior effects than sleeve gastrectomy in cardiovascular metabolism and hypertension5. The two surgical techniques are anatomically distinct and have different effects on weight regulation, leading to varying degrees of cardiovascular effects. Whether these three systematic reviews provide a stratified analysis or comparison of the antihypertensive effects on different bariatric surgery techniques is an indispensable part of the methodological appraisal. We admire and commend this work, as it systematically assessed the quality and certainty of evidence on the effect of bariatric surgery in patients with nonmorbid obesity and hypertension. Although the research conclusively shows that the methodological quality of systematic reviews is critically low overall, metabolic surgery is undeniably an effective intervention for the treatment of obesity and hypertension. We hope our opinions can help to promote the quality of research and facilitate updates to systematic reviews. More and more high-quality clinical studies are expected to provide stronger evidence-based support for metabolic surgery in the treatment of hypertension. Ethical approval Not applicable. Sources of funding None. Authors’ contribution X.S. and Y.W. designed the study. X.S. wrote the manuscript. Y.H. reviewed and revised the manuscript. All authors contributed to the article and approved the submitted version. Conflicts of interest disclosure The authors declare that they have no financial conflict of interest with regard to the content of this report. Research registration unique identifying number (UIN) None. Guarantor All authors.